Screw thread connection for electric light bulbs and sockets



y 16, 0- A. ILLSCHE 2,208,423

SCREW THREAD CONNECTION FOR ELECTRIC LIGHT BULBS AND SOCKETS Filed Jan.15, 1940 2 Sheets-Sheet l fi nz'- L 5 III] I I I I a I 9 4 0 2 z July16, 1940. 2,208,423

SCREW THREAD CONNECTION FOR ELECTRIC LIGHT BULBS AND SOCKETS Filed Jan.15, 1940 2 Sheets-Sheet 2 Patented July 16, 1940 PATENT OFFICE SCREWTHREAD CONNECTION FOR ELEC- TRIC LIGHT BULBS AND SOCKETS Arthur Illsche,Rye, N. Y. Application January 15, 1940, Serial No. 313,917

4 Claims.

This invention relates to terminal screw caps and sockets for electriclight bulbs, socket plugs, fuse plugs and the like.

Screw caps for light bulbs or plugs and the sockets for the same, now incommon use, are provided with shallow rounded threads of four or five ormore turns that are loose fitting until completely engaged and requirerotation through an objectionable number of revolutions before suchcomplete engagement is effected. Unless given a final hard turn, tofrictionally bind the threaded bulb cap in the socket, poor electricalcontact will result from the insecure connection, causing the light tovary more or it less and if subjected to vibration, as frequentlyhappens, the connection will be further loosened until the circuit iscompletely broken and the light extinguished.

Difficulty is also experienced in preliminarily 29 engaging the threadsof the bulb or plug cap and the socket, as the threads are of uniformdiameter throughout their length, which makes it necessary to positionthe bulb or plug in exact axial alignment with the socket, beforeengagement can be effected and this can only be accomplished,ordinarily, after repeated unsuccessful efforts and frequently has to bedone blindly, as the socket, while accessible, is in many instances,concealed from view. As no mechanical aid is provided to bring themembers into centered relation, the operation proves difficult, annoyingand a severe trial to the patience of the great majority of people whohave very little if any mechanical skill or ability.

My invention is designed to avoid the above and other objectionablefeatures of present day light bulbs, plugs and sockets, by first,effecting complete engagement by rotation through less than a singlerevolution; second, by shaping the threaded portions of the bulb or plugand the socket to enter freely one within the other to substantiallytheir full length, in nested, centered relation, preparatory to engagingthe threads and third, by giving the thread a coarse, deep, closefitting form, that will insure permanence in the connection against theaction of vibration and maintenance of good electrical contact in thecurrent supply circuit to the lamp.

The accompanying drawings will serve to illustrate a constructionsuitable for carrying the invention into effect but I do not wish to beunderstood as intending to limit myself to the formed and ifnon-conducting, provided with requisite metal contacts, as will beobvious.

In the drawings- Fig. 1 is a view in elevation, partly in section,showing the invention applied to an electric bulb 5 and socket.

Fig. 2 shows the lower portion of the bulb vieweld from the sideopposite that shown in Fig.

b Fig. 3 is a view looking at the bottom of the 10 ulb.

Fig. 4 is a top plan view of the socket.

Fig. 5 is a view in elevation showing the invention applied to a fuseplug, and

Fig. 6 is a like view,. showing the application 15 to a socket plug,

Referring to the drawings, I indicates an electric light bulb and 2 asocket .for the same. The bulb and socket will be recognized as wellknown types now in common use and need not, therefore, be described indetail.

The main departure from the art is in the form of the means employed toseparably connect the bulb and socket. To meet practical requirements,the connection must be such as to provide 25 safe and secure support forthe bulb, which is ordinarily positioned in pendant relation to thesocket and also to insure maintenance of good electrical contact in thecircuit connections for the supply of current to the lamp. 30

Counterpart screw threads 3 and 4 are employed for the connection and asformed, not only meet the above requirements, but go further, to greatadvantage in enabling the cooperating threads to be instantly broughtinto en- 5 gaging relation without hesitation, uncertainty or thepossibility of failure, ready to be secured in interlocked engagement byrelative rotation through approximately half a revolution.

The terminal metal cap 5, cemented or otherwise secured to the bulb,serves as one threaded member of the connection and the other, itscounterpart 6, is positioned and fixed in the open end of the socket, asillustrated in Fig. 1, where the cooperating threads are shown engaged,clos- 5 ing the circuit through the bulb, in the usual manner.

In general outline, the threaded members 5 and 6, are of frustro-conicalform, being tapered and terminating in blunt ends 1 and 8 and thusformed, the male member 5 is freely enterable into the counterpart 6',in nested relation, to almost its full length, before being rotated tobring about engagement of the threads.

This free entrance of one threaded member into the other tosubstantially fulldepth, resulting from the tapered guide form given themembers, enables the lamp bulb to not only be definitely positioned butheld in centered relation in the socket, ready to be given the half turnthat interlocks the threads.

This mechanical aid in the preliminary positioning of the members, sogreatly simplifies the operation of putting in" a bulb, that no skill ormechanical ability is required and any one can do it instantly andblindly from the sense of touch alone. 7

In the preferred form, the thread is of a length sufllclent to makeabout two turns on the carrying member. One face 9 of the thread isnarrow and the other face l0, broad. The narrow face is approximatelyperpendicular to the axis of the conical carrier and of substantiallyuniform width throughout the greater portion of its length. The broadface, developed from practically zero dimensions at the small end of theconical carrier, is gradually enlarged to a width several times that ofthe narrow face.

The narrow face of the thread serves to effectively lock the connectionagainst accidental disengagement and the broad face gives strength andsteadiness to the connection and its extended surface area insures agood electrical contact on the ground side of the lamp circuit.

The threaded socket member 6 is open at its smaller end to expose thecommonly employed spring contact member H. The threaded bulb cap 5 isclosed at its smaller end by the usual insulated metal terminal inserti2, connected with the positive side of the lamp filament, as indicatedby the dotted line l3. The lead from the opposite side of the filamentis connected to the bulb cap, as indicated by the dotted line ll.

When the threaded members are engaged, as shown in Fig. 1, the terminalI2 engages and depresses the spring contact H, completing the,

lamp circuit through the filament, in the usual manner.

,From the foregoing it will be apparent that the invention may beapplied with equal advantage to fuse plugs, as shown in Fi 5. socketplugs, as shown in Fig. 6, and to other circuit closing elements, wheredifficulty is experienced or delay is met with readily engaging theelements to close the circuit.

Having described my invention, I claim:

1. A connection for supporting an electrical device and closing acircuit through the same,

comprising two members having engaging pora,aos,4as

tions offrustro-conical form, the taper of which is such as to permitentry of one into the other in nested self-centering relation tosubstantially their full length, screw-threads thereon extendingthroughout said frustro-conlcal portions and so formed that relativerotation of the members through less than a revolution effects completeinterlocking engagement between the threads, the contacting surfaces ofwhich close one side of a circuit through the supported device, one ofthe members being open at the smaller end and the other member closed byan insulated terminal projecting into said open end of the firstmentioned member to close and complete the circuit through the supporteddevice.

2. An electrical plug and socket connection comprising two membershaving screw threads thereon, one face of the thread being approximatelyperpendicular to the common axis of the engaged members and the oppositeface of the thread inclined to the axis, the formation being such thatrelative rotation of the members through less than a complete revolutioneffects complete interlocking engagement between the threads, thecontacting surfaces of which close one side of a circuit through themembers; the engaging portion of one of the members being at its smallerend and the engaging portion of the other member closed by an insulatingterminal projecting into said open end to close and complete thecircuit.

3. An electrical plug and socket connection comprising two engageablemembers having screw threads thereon, one face of each thread beingapproximately perpendicular to the common axis of the engaged membersand of substantially uniform width throughout the greater portion of itslength and the opposite face inclined to the axis and graduallyincreasing throughout its length to a widthgreater than that of thenarrow face to provide broad contacting surfaces for passage of currentthrough the members.

4. A screw thread connection, as defined in claim 3, in which the faceof the thread disposed at an angle to the common axis of the members isdeveloped within an approximate two-turn length of the thread fromsubstantially zero dimensions to more than double the width of theopposite face thereof to provide broad contacting surfaces as part ofthe metallic circuit. through which current is supplied through theconnection.

- ARTHUR ILLSCHE.

